Can never win in low ELO

So over the course of my LoL lifespan I've found that playing support is generally my best role. I perform the best in that role and I usually queue as support/mid or fill. This past week I have been accused 5 times with some variation of "only playing support expecting to get carried because you suck." So if I get flamed for not playing well in other roles, and I get flamed for playing support, what do people expect me to do? lol. in my previous game a level 5 kindred attempted to fight a level 7 lulu and level 8 caitlyn while I sat at my tower with around 300 hp and 100 mana as alistar. She proceeded to tell me that if I had gone in we could have got a double, and that I suck and should go practice on bots.

Generally there is a person like this in 80% of my games. I usually just say something like "ahhh.. silver" or "ok lol" in the chat. There are certain occasions where I get frustrated and flame them back, which is my mistake and I know its wrong.

Since I started playing league again, I managed to climb to gold 4 or 3 my first 2 weeks of ranked playing 90% support, and I believe a curse befell me because I have dropped back as low as silver 4, and am now in an eternal promotion/demotion loop. I get up to silver 2 with utmost difficulty might I add, I then end up losing 2-3 games after my promotion, I win maybe 1 or 2, then I lose 3-4 more and get demoted. After the demotion, I am tilted and end up dropping back down to around 20-30 LP before I stop playing for a few days, and the cycle repeats itself.

What abvice would anyone have for a support main to increases my chances of victory from game to game?